#!/usr/bin/env bash

(($# > 1)) && { echo >&2 "usage: $0 [<version file>]"; exit 1; }
GVF="$1"

DEF_VER="unnamed_version"
LF='
'

# First see if there is a version file (included in release tarballs),
# then try git-describe, then gitweb, then default.
if [[ -f VERSION ]]; then
	VN=$(cat VERSION) || VN="$DEF_VER"
elif [[ -d .git || -f .git ]] &&
	VN=$(git describe --abbrev=4 HEAD 2>/dev/null) &&
	case "$VN" in
	*$LF*) (exit 1) ;;
	v[0-9]*)
		git update-index -q --refresh &>/dev/null
		test -z "$(git diff-index --name-only HEAD --)" ||
		VN="$VN-dirty" ;;
	esac
then
	VN=$(echo "$VN" | sed -e 's/-/./g');
elif [[ "$PWD" =~ paraslash-[a-f0-9]{1,} ]]; then
	VN="${PWD#*-}"
else
	VN="$DEF_VER"
fi

VN=$(expr "$VN" : v*'\(.*\)')
echo "$VN"

[[ -z "$GVF" ]] && exit 0
if [[ -r "$GVF" ]]; then
	pattern='^#define GIT_VERSION "'
	VC=$(grep "$pattern" < "$GVF" | sed -e "s/$pattern//; s/\"$//")
	[[ "$VN" == "$VC" ]] && exit 0
fi
echo >&2 "new git version: $VN"
echo "/** \\file ${GVF##*/} Auto-generated version file. Do not edit. */" >$GVF
echo "#define GIT_VERSION \"$VN\"" >> $GVF